The invention relates to a device for reproducing a luminance signal from a magnetic record carrier in tracks which are inclined relative to the longitudinal direction of said record carrier, the speed of transport of the record carrier during reproduction being different from that during recording and a time error of approximately half a line period being introduced in the signal being read at every transition from a track read by a reproducing head to a following track to be read by the same head, which device comprises
a first correction circuit for correcting said time error in response to a first control signal, and
a second correction circuit for the compensation of dropouts in the signal read from the tracks in response to a second control signal,
the first correction circuit comprising a first switching unit having a control-signal input to receive the first control signal, a first and a second input, and an output, and a first delay line, an input of the first correction circuit being coupled to the first input and, via the first delay line, to the second input of the first switching unit, the output of the first switching unit being coupled to the output of the first correction circuit,
the second correction circuit comprising a second switching unit having a control input to receive the second control signal, a first and a second input, and an output, and a second delay line, an input of the second correction circuit being coupled to the first input of the second switching unit, and the second delay line being coupled to the second input of the second switching unit, whose output is coupled to the output of the second correction circuit.
From German Offenlegungsschrift No. 2,232,361, it is known to provide a device for reproducing a video signal from a record carrier whose tracks are inclined relative to the longitudinal direction of the record carrier with a (second) correction circuit to provide compensation for dropouts in the signal read from the tracks. To this end the device comprises a dropout detector which supplies a (second) control signal at the instant at which a dropout is detected. Under the influence of this control signal the (second) switching unit in the correction circuit is changed over, causing a signal delayed by the (second) delay line to be applied to the output of the (second) correction circuit. The (second) delay line, which provides a delay equal to the line period of the video signal, may be arranged between the input of the (second) correction circuit and the second input of the (second) switching unit, or between the output and the second input of the second switching unit. In the last-mentioned case the delay line forms a feedback system, so that the (second) correction circuit is also capable of compensating for longer dropouts.
When a video signal is recorded at the normal record-carrier speed (short play) in tracks which are inclined relative to the longitudinal direction of the record carrier, the successive tracks have an offset of 1.5 line relative to one another, see for example German Offenlegungsschrift No. 2,939,276, FIG. 2. Since each track contains 312.5 lines of a picture this means that the horizontal synchronizing signals in adjacent tracks are also situated adjacent one another.
During reproduction at a record-carrier speed which differs from that during recording (features) the reproducing head follows a line which intersects the tracks across the record carrier. During a transition from a track being read to another track to be read this means that no time errors occur between the signals read from the two tracks.
This is different if a video signal is recorded at a record-carrier speed lower than the aforementioned normal speed (long play). If this speed is half the normal speed, which means that the playing time is doubled, the successive tracks will be recorded with an offset of 0.75 line relative to one another on the record carrier. A result of this is that during reproduction at a record-carrier speed which differs from the speed during recording (features) a time error arises between the signals successively read from two tracks by a reproducing head.
Currently available video recorders are generally provided with two reproducing heads having mutually different azimuth angles and arranged at 180.degree. from one another on a rotary head drum. One reproducing head then reads every second track and the other reproducing head reads the intermediate tracks. The time error between the signals successively read from two tracks by a reproducing head is therefore equal to half the line period, or 32 .mu.s. The first correction circuit provides correction for this time error.
It is known to construct the first delay line in the first correction circuit as a 32 .mu.s glass delay line.
Another method of realizing the first delay line is to use a charge-coupled device (CCD). This device serves to delay the combined chrominance and luminance signal and for this purpose it is operated with a clock frequency of for example 3.f.sub.s, f.sub.s being the subcarrier frequency, which is 4.43 MHz for PAL. However, both solutions are expensive.